What darkened the South Pacific northeast of Australia on May 10, as seen by NASA’s Terra satellite? (Image: NASA)

What’s up with that brown splotch sprawling across a broad swath of the South Pacific in the upper right corner of this satellite image?

Nope, it’s not some black hole that has just materialized in the middle of the ocean, threatening to suck New Guinea and Australia into its depths. Neither is a gargantuan oil spill, or a massive bubble of air pollution that’s drifted in from China.

What happened on May 10 northeast of Australia was completely natural and unthreatening: an annular eclipse of the sun. When this kind of eclipse happens, the moon passes in front of the sun, but it doesn’t black it out completely. That’s why the shadow cast onto the ocean in this image captured by NASA Terra satellite is not completely black and opaque. Some sunlight is getting through, producing more of a brown-out. (The black stripes are areas not imaged by Terra.)

Here’s what the X-Ray Telescope on the Hinode spacecraft saw when the moon passed between it and the sun:

The annular eclipse of the Sun as seen on May 10 by the Hinode spacecraft. Click for a detailed explanation. (Animation: XRT Picture of the Week — SAO, NASA, JAXA, NAOJ)

In an annular eclipse, the moon lines up in just the right way to allow only a fiery ring to be seen around its dark disk. That wasn’t the case here because Hinode was seeing the sun from a perspective in which the moon wasn’t perfectly aligned.

Lastly, here’s an image from closer to home:

A close-up from the Terra satellite of the South Pacific as the annular eclipse occurred. (Image: NASA)

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ImaGeo

ImaGeo is a visual blog focusing on the intersection of imagery, imagination and Earth. It focuses on spectacular visuals related to the science of our planet, with an emphasis (although not an exclusive one) on the unfolding Anthropocene Epoch.

About Tom Yulsman

Tom Yulsman is Director of the Center for Environmental Journalism and a Professor of Journalism at the University of Colorado, Boulder. He also continues to work as a science and environmental journalist with more than 30 years of experience producing content for major publications. His work has appeared in the New York Times, Washington Post, Audubon, Climate Central, Columbia Journalism Review, Discover, Nieman Reports, and many other publications. He has held a variety of editorial positions over the years, including a stint as editor-in-chief of Earth magazine. Yulsman has written one book: Origins: the Quest for Our Cosmic Roots, published by the Institute of Physics in 2003.